Transmission-Based Temperature Measurement of a Workpiece in a Thermal Processing System

ABSTRACT

A thermal processing system for performing thermal processing can include a workpiece support plate configured to support a workpiece and heat source(s) configured to heat the workpiece. The thermal processing system can include window(s) having transparent region(s) that are transparent to electromagnetic radiation within a measurement wavelength range and opaque region(s) that are opaque to electromagnetic radiation within a portion of the measurement wavelength range. A temperature measurement system can include a plurality of infrared emitters configured to emit infrared radiation and a plurality of infrared sensors configured to measure infrared radiation within the measurement wavelength range where the transparent region(s) are at least partially within a field of view the infrared sensors. A controller can be configured to perform operations including obtaining transmittance and reflectance measurements associated with the workpiece and determining, based on the measurements, a temperature of the workpiece less than about 600° C.

PRIORITY CLAIM

The present application claims the benefit of priority of U.S.Provisional Application Ser. No. 62/983,064, titled Transmission-BasedTemperature Measurement of a Workpiece in a Thermal Processing System,filed on Feb. 28, 2020, which is incorporated herein by reference.

FIELD

The present disclosure relates generally to thermal processing systems,such as thermal processing systems operable to perform thermalprocessing of a workpiece.

BACKGROUND

A thermal processing chamber as used herein refers to a device thatheats workpieces, such as semiconductor workpieces (e.g., semiconductorworkpieces). Such devices can include a support plate for supporting oneor more workpieces and an energy source for heating the workpieces, suchas heating lamps, lasers, or other heat sources. During heat treatment,the workpiece(s) can be heated under controlled conditions according toa processing regime.

Many thermal treatment processes require a workpiece to be heated over arange of temperatures so that various chemical and physicaltransformations can take place as the workpiece is fabricated into adevice(s). During rapid thermal processing, for instance, workpieces canbe heated by an array of lamps through the support plate to temperaturesfrom about 300° C. to about 1,200° C. over time durations that aretypically less than a few minutes. During these processes, a primarygoal can be to reliably and accurately measure a temperature of theworkpiece.

SUMMARY

Aspects and advantages of embodiments of the present disclosure will beset forth in part in the following description, or may be learned fromthe description, or may be learned through practice of the embodiments.

One example aspect of the present disclosure is directed to a thermalprocessing system for performing thermal processing of semiconductorworkpieces. The thermal processing system can include a workpiecesupport plate configured to support a workpiece. The thermal processingsystem can include one or more heat sources configured to heat theworkpiece. The thermal processing system can include one or more windowsdisposed between the workpiece support plate and the one or more heatsources. The one or more windows can include one or more transparentregions that are transparent to at least a portion of electromagneticradiation within a measurement wavelength range and one or more opaqueregions that are opaque to electromagnetic radiation within the portionof the measurement wavelength range.

These and other features, aspects and advantages of various embodimentswill become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the present disclosure and, together with thedescription, serve to explain the related principles.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed discussion of embodiments directed to one of ordinary skill inthe art are set forth in the specification, which makes reference to theappended figures, in which:

FIG. 1 depicts an example thermal processing system according to exampleaspects of the present disclosure;

FIG. 2 depicts an example thermal processing system configured tomeasure an emissivity of a workpiece according to example aspects of thepresent disclosure;

FIG. 3 depicts an example thermal processing system configured tomeasure a temperature of a workpiece according to example aspects of thepresent disclosure;

FIG. 4 depicts an example temperature measurement system according toexample aspects of the present disclosure;

FIG. 5A depicts a transmittance plot for an example opaque regionmaterial according to example aspects of the present disclosure;

FIG. 5B depicts a transmittance plot for an example transparent regionmaterial according to example aspects of the present disclosure;

FIG. 6A depicts a transmittance plot for example workpiece typesaccording to example aspects of the present disclosure;

FIG. 6B depicts a transmittance plot of example normalized workpiecetransmittance according to example aspects of the present disclosure;

FIG. 7 depicts a method for temperature measurement of a workpiece in athermal processing system according to example aspects of the presentdisclosure; and

FIG. 8 depicts a method for calibrating a reference intensity forsensors in a thermal processing system according to example aspects ofthe present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments, one or moreexamples of which are illustrated in the drawings. Each example isprovided by way of explanation of the embodiments, not limitation of thepresent disclosure. In fact, it will be apparent to those skilled in theart that various modifications and variations can be made to theembodiments without departing from the scope or spirit of the presentdisclosure. For instance, features illustrated or described as part ofone embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that aspects of the presentdisclosure cover such modifications and variations.

Example aspects of the present disclosure are directed to thermalprocessing systems, such as rapid thermal processing (RTP) systems forworkpieces, such as semiconductor workpieces (e.g., silicon workpieces).In particular, example aspects of the present disclosure are directed toobtaining a temperature measurement indicative of a temperature of atleast a portion of a workpiece within a thermal processing system. Forexample, a temperature measurement can be useful in monitoring atemperature of a workpiece while thermal processing is being performedon the workpiece.

Example aspects of the present disclosure can be particularly beneficialin obtaining a temperature measurement at workpiece temperatures atwhich a workpiece is substantially transparent and/or does not emitsignificant blackbody radiation. In some cases, it can be difficult tomeasure a workpiece temperature at around these temperatures byconventional methods. In particular, some workpieces, such asnon-metallized workpieces (e.g., lightly doped silicon workpieces) canbe difficult to measure a temperature of by conventional methods belowabout 600° C. For instance, the workpieces can be substantiallytransparent to many wavelengths conventionally used for transmittancemeasurement at temperatures below about 600° C. Furthermore, theworkpieces can be too cold to emit practically measurable blackbodyradiation at conventional wavelengths.

Example aspects of the present disclosure can thus allow for accuratetransmittance-based and emissivity-compensated temperature measurementof a workpiece at low temperatures, such as below about 600° C., such asfrom about 400° C. to 600° C. Additionally, sensors used in obtainingthe transmittance-based temperature measurement for workpiecetemperatures below about 600° C. can be repurposed and/or also used foremission-based temperature measurement of a workpiece for workpiecetemperatures at which the workpiece is substantially opaque and/or emitssignificant blackbody radiation, such as above about 600° C.Additionally, measurement wavelengths and/or other process aspects,including phase-locking of certain measurements, can be selected tominimize interference between various functions of the thermalprocessing systems. This can allow for systems and methods according toexample aspects of the present disclosure to measure temperatures overan increased range, such as an increased range including temperaturesbelow about 600° C., compared to conventional systems and methods.Additionally, this can allow systems and methods to smoothly transitionfrom a transmittance-based temperature measurement for temperatures atwhich the workpiece does not emit practically measurable blackbodyradiation (e.g., below about 600° C.) to an emission-based temperaturemeasurement for temperatures at which the workpiece emits measurableradiation (e.g., above about 600° C.) without requiring additionalsensors and/or reconfiguration of the sensors, as the same sensors usedfor the transmittance-based temperature measurement can be used for theemission-based temperature measurement, such as once the workpiece is nolonger at least partially transparent.

According to example aspects of the present disclosure, a thermalprocessing system, such as a rapid thermal processing system, caninclude a workpiece support plate configured to support a workpiece. Forexample, a workpiece can be a workpiece, such as a substrate, to beprocessed by a thermal processing system. A workpiece can be or includeany suitable workpiece, such as a semiconductor workpiece, such as asilicon workpiece. In some embodiments, a workpiece can be or include alightly doped silicon workpiece. For example, a lightly doped siliconworkpiece can be doped such that a resistivity of the silicon workpieceis greater than about 0.1 Ωcm, such as greater than about 1 Ωcm.

A workpiece support plate can be or can include any suitable supportstructure configured to support a workpiece, such as to support aworkpiece in a thermal processing chamber of a thermal processingsystem. In some embodiments, a workpiece support plate can be configuredto support a plurality of workpieces for simultaneous thermal processingby a thermal processing system. In some embodiments, a workpiece supportplate can be or include a rotating workpiece support configured torotate a workpiece while the workpiece is supported by the rotatingworkpiece support plate. In some embodiments, the workpiece supportplate can be transparent to and/or otherwise configured to allow atleast some electromagnetic radiation to at least partially pass throughthe workpiece support plate. For instance, in some embodiments, amaterial of the workpiece support plate can be selected to allow desiredelectromagnetic radiation to pass through the workpiece support plate,such as electromagnetic radiation that is emitted by a workpiece and/oremitters and/or measured by sensors in a thermal processing system. Insome embodiments, the workpiece support plate can be or include a quartzmaterial.

According to example aspects of the present disclosure, a thermalprocessing system can include one or more heating sources (e.g., heatinglamps) configured to heat a workpiece. For example, one or more heatinglamps can emit electromagnetic radiation (e.g., broadbandelectromagnetic radiation) to heat a workpiece. In some embodiments, oneor more heating lamps can be or include, for example, arc lamps,tungsten-halogen lamps, and/or any other suitable heating lamp, and/orcombination thereof. In some embodiments, directive elements such as,for example, reflectors (e.g., mirrors) can be configured to directelectromagnetic radiation from one or more heating lamps towards aworkpiece and/or workpiece support plate.

According to example aspects of the present disclosure, a thermalprocessing system can include a temperature measurement systemconfigured to measure a temperature of a workpiece in the thermalprocessing system. For instance, the temperature measurement system caninclude a plurality of radiation sensors (e.g., infrared sensors)configured to measure electromagnetic radiation at various points in athermal processing system (e.g., in a thermal processing chamber).Additionally and/or alternatively, the temperature measurement systemcan include a plurality of radiation emitters (e.g., infrared emitters)configured to emit electromagnetic radiation into a thermal processingsystem (e.g., a thermal processing chamber) that passes through variouscomponents in the thermal processing system, such as the workpiece,chamber windows, workpiece support plate, and/or other suitablecomponents. Based on the radiation emitted by the emitters and/ormeasured by the sensors, the temperature measurement system candetermine (e.g., estimate) a temperature of the workpiece, as discussedmore particularly below. For instance, as one example of atransmittance-based temperature measurement, a transmittance determinedfor a portion of a workpiece can be compared against a transmittancecurve, such as a normalized transmittance curve, to determine atemperature of the portion of the workpiece. As one example of anemission-based temperature measurement, the temperature T of theworkpiece can be determined based on radiation emitted by the workpiece,I_(wafer), according to the following equation:

$T = {\frac{hc}{\lambda k} \cdot \frac{1}{\ln\left( {{\frac{2\pi{hc}^{2}\Delta\lambda}{\lambda^{5}} \cdot \frac{\varepsilon}{I_{Wafer}}} + 1} \right)}}$

According to example aspects of the present disclosure, a thermalprocessing system (e.g., a temperature measurement system) can include aplurality of infrared emitters. Infrared emitters can be configured toemit electromagnetic radiation at one or more infrared wavelengths(e.g., wavelengths from about 700 nanometers to about one millimeter).For instance, infrared emitters can emit infrared radiation directed atleast partially at a workpiece. At least a portion of infrared radiationdirected at a workpiece can be transmitted through the workpiece.Furthermore, at least a portion of infrared radiation directed at aworkpiece can be reflected by the workpiece. In some embodiments,infrared emitters can be positioned outside of a workpiece processingchamber. For example, the infrared emitters positioned outside of aworkpiece processing chamber can emit radiation such that the radiationfirst passes through a chamber sidewall (e.g., a chamber window) priorto passing through a workpiece. In some embodiments, the infraredemitters can be disposed inline with an array of heating elements (e.g.,heating lamps). Additionally and/or alternatively, the infrared emitterscan be disposed closer to and/or farther from a workpiece than theheating lamps.

According to example aspects of the present disclosure, a thermalprocessing system can include a plurality of infrared sensors. Infraredsensors can be configured to obtain a measurement of electromagneticradiation, such as electromagnetic radiation having an infraredwavelength, incident on the infrared sensors. In some embodiments,infrared sensors can be or include a pyrometer. In some embodiments, apyrometer can be or include a dual-head pyrometer that includes a firsthead configured to measure a first wavelength of infrared radiation anda second head configured to measure a second wavelength of infraredradiation. In some embodiments, the first wavelength and/or the secondwavelength can be within the measurement wavelength range. In someembodiments, the first wavelength can be about 2.3 micrometers and/orthe second wavelength can be about 2.7 micrometers.

According to example aspects of the present disclosure, one or morewindows (e.g., chamber windows) can be disposed between a workpieceand/or a workpiece support plate and one or more heating lamps. One ormore chamber windows can be configured to selectively block at least aportion of electromagnetic radiation (e.g., broadband radiation) emittedby one or more heating lamps from entering a portion of a thermalprocessing chamber (e.g., being incident on a workpiece and/or aworkpiece support plate and/or one or more sensors). For example, one ormore chamber windows can include one or more opaque regions and/or oneor more transparent regions. As used herein, “opaque” means generallyhaving a transmittance of less than about 0.4 (40%) for a givenwavelength, and “transparent” means generally having a transmittance ofgreater than about 0.4 (40%) for a given wavelength.

The one or more opaque regions and/or one or more transparent regionscan be positioned such that the opaque regions block stray radiation atsome wavelengths from the heating lamps, and the transparent regionsallow, for example, emitters and sensors to freely interact withradiation in the thermal processing chamber at the wavelengths blockedby the opaque regions. In this way, the windows can effectively shieldthe emitters and sensors from contamination by the heating lamps whilestill allowing the heating lamps to heat the workpiece. The one or moreopaque regions and one or more transparent regions can generally bedefined as opaque and transparent, respectively, to a particularwavelength; that is, for at least electromagnetic radiation at theparticular wavelength, the opaque regions are opaque and the transparentregions are transparent. For example, in some embodiments, thetransparent regions can be transparent to at least a portion ofelectromagnetic radiation within a measurement wavelength range. In someembodiments, the opaque regions can be opaque to at least a portion ofelectromagnetic radiation within a measurement range. A measurementrange can be or include a wavelength for which an intensity ofelectromagnetic radiation is measured by at least one sensor in thethermal processing system.

One or more chamber windows, including one or more opaque regions and/orone or more transparent regions, can be formed of any suitable materialand/or construction. In some embodiments, one or more chamber windowscan be or include a quartz material. Furthermore, in some embodiments,one or more opaque regions can be or include hydroxyl (OH) containingquartz, such as hydroxyl doped quartz (e.g., quartz that is doped withhydroxyl), and/or one or more transparent regions can be or includehydroxyl free quartz (e.g., quartz that is not doped with hydroxyl).Advantages of hydroxyl doped quartz and hydroxyl free quartz can includean ease of manufacturing. For instance, the hydroxyl free quartz regionscan be shielded during hydroxyl doping of a monolithic quartz window toproduce both hydroxyl doped regions (e.g., opaque regions) and hydroxylfree regions (e.g., transparent regions) in the monolithic window.Additionally, hydroxyl doped quartz can exhibit desirable wavelengthblocking properties in accordance with the present disclosure. Forinstance, hydroxyl doped quartz can block radiation having a wavelengthof about 2.7 micrometers, which can correspond to a measurementwavelength at which some sensors in the thermal processing systemoperate, while hydroxyl free quartz can be transparent to radiationhaving a wavelength of about 2.7 micrometers. Thus, the hydroxyl dopedquartz regions can shield the sensors from stray radiation in thethermal processing system (e.g., from the heating lamps), and thehydroxyl free quartz regions can be disposed at least partially within afield of view (e.g., a region for which the sensors are configured tomeasure infrared radiation) of the sensors to allow the sensors toobtain measurements within the thermal processing system. Additionally,hydroxyl doped quartz can be partially opaque (e.g., have atransmittance around 0.6, or 60%) to radiation having a wavelength ofabout 2.3 micrometers, which can at least partially reduce contaminationfrom stray radiation in the thermal processing system (e.g., from theheating lamps).

Infrared radiation emitted by an infrared emitter and/or measured by aninfrared sensor can have one or more associated wavelengths. Forinstance, in some embodiments, an infrared emitter can be or include anarrow-band infrared emitter that emits radiation such that a wavelengthrange of the emitted radiation is within a tolerance of a numericalvalue, such as within 10% of the numerical value, in which case theemitter is referred to by the numerical value. In some embodiments, thiscan be accomplished by a combination of a wideband emitter that emits awideband spectrum (e.g., a Planck spectrum) and an optical filter, suchas an optical notch filter, configured to pass only a narrow band withinthe wideband spectrum. Similarly, an infrared sensor can be configuredto measure an intensity of infrared narrow-band infrared radiation at(e.g., within a tolerance of) a numerical value. For example, in someembodiments, an infrared sensor, such as a pyrometer, can include one ormore heads configured to measure (e.g., select for measurement) aparticular narrow-band wavelength.

In some embodiments, infrared radiation emitted by an infrared emitterand/or measured by an infrared sensor can be within a measurementwavelength range, which may be or include a continuous range and/or anoncontinuous range. The measurement wavelength range can be selectedbased on characteristics of a workpiece and/or a workpiece processingsystem. For example, the measurement wavelength range can includewavelengths that a workpiece and/or transparent regions in one or morechamber windows are transparent to for at least temperatures less thanabout 600° C. Additionally and/or alternatively, the measurementwavelength range can include wavelengths that opaque regions in one ormore chamber windows are opaque to for at least temperatures less thanabout 600° C. In this manner, the emitters can emit radiation that issubstantially transmitted through the transparent regions and at leastpartially protected, by the opaque regions, from contamination byheating lamps before being incident on the sensors. Although it can bedesirable, in some embodiments, to eliminate contamination by heatinglamps in the measurement wavelength range, the measurement wavelengthrange can nonetheless include wavelengths having contamination fromheating lamps(e.g., wavelengths that can at least partially pass throughthe opaque regions). Additionally and/or alternatively, the measurementwavelength range can include wavelengths at which a workpiece emitssignificant (e.g., measurable) blackbody radiation for at leasttemperatures greater than about 600° C. In some embodiments, themeasurement wavelength range can include about 2.3 micrometers and/orabout 2.7 micrometers. For instance, in some embodiments, one or moreinfrared sensors can be configured to measure an intensity of infraredradiation in a field of view of the sensor at about 2.3 micrometers.Similarly, one or more infrared sensors can be configured to measure anintensity of infrared radiation in a field of view of the sensor atabout 2.7 micrometers.

In some embodiments, a temperature measurement system can include anemissivity measurement system configured to measure (e.g., estimate)emissivity of a workpiece. As one example of measuring emissivity of aworkpiece, an emissivity measurement system can include an infraredemitter configured to emit infrared radiation directed toward aworkpiece. In some embodiments, the infrared emitter can emit infraredradiation directed at an oblique angle towards a surface of a workpiece(e.g., at an angle less than 90 degrees from the surface of theworkpiece). In this manner, a transmitted portion of the emittedradiation can be transmitted through the workpiece and a reflectedportion of the emitted radiation can be reflected by the surface of theworkpiece. An angle of reflection for the reflected portion can bepredicted and/or known based on characteristics of the workpiece.Infrared sensors can be positioned to measure the transmitted portionand/or the reflected portion. Based at least in part on the firstportion and/or the second portion, the emissivity measurement system candetermine emissivity of a workpiece. In some embodiments, the emissivitymeasurement system, such as the emitter and/or the sensors, can operateat a first wavelength of a measurement wavelength range. For instance,the first wavelength can be a wavelength at which the transparentregions of the chamber windows are transparent and/or the opaque regionsare opaque. In some embodiments, the first wavelength can be or includeabout 2.7 micrometers.

Additionally and/or alternatively, a thermal processing system (e.g., atemperature measurement system) can include a transmittance measurementsystem. The transmittance measurement system can be configured to obtainone or more transmittance measurements of a workpiece. For example, insome embodiments, the transmittance measurement system can obtain acenter transmittance measurement of a center portion of a workpiece(e.g., by a center sensor, such as a center pyrometer) and an edgetransmittance measurement of an edge portion of the workpiece (e.g., byan edge sensor, such as an edge pyrometer). In some embodiments, thetransmittance measurement system can include one or more infraredemitters configured to emit infrared radiation directed orthogonally toa surface of a workpiece. Additionally, the transmittance measurementsystem can include one or more infrared sensors disposed opposite theone or more infrared emitters and configured to measure a portion of theinfrared radiation emitted by the one or more infrared emitters andpassing through the workpiece.

It can be possible to determine a temperature of a workpiece based ontransmittance of the workpiece. However, transmittance of a workpiece isnot correlated with only temperature. For instance, workpiececharacteristics such as, for example, bulk doping levels, reflectiveproperties of the workpiece surface, and workpiece thickness can allaffect transmittance. As such, a temperature measurement system can, insome embodiments, determine a normalized transmittance measurementcorrelated with workpiece temperature. For example, the normalizedtransmittance measurement can range from 0 to 1, regardless of workpiececharacteristics.

Additionally and/or alternatively, sensor measurements used to determinetransmittance of a workpiece can be impacted by other components in thechamber, such as, for example, a workpiece support plate, chamberwindows, and/or any other components, and especially components thatmust pass infrared radiation emitted by an emitter and measured by asensor. According to example aspects of the present disclosure, athermal processing system (e.g., a temperature measurement system), candetermine a reference intensity, denoted herein as I₀, for each of oneor more sensors in the thermal processing system. A reference intensitycan correspond to radiation emitted by an emitter and/or incident on asensor when a workpiece is not present in the processing chamber. Inother words, the reference intensity can be diminished from theintensity of radiation emitted by an emitter only by contributions fromcomponents other than the workpiece in the thermal processing system.This can additionally correspond to a case of 100% transmittance by aworkpiece. In some embodiments, the reference intensity can be measuredprior to insertion of a workpiece in the processing chamber, such asbetween thermal processing of two workpieces.

In some embodiments, the transmittance measurement system can operate ata same wavelength as an emissivity measurement system (e.g., the firstwavelength). Additionally and/or alternatively, the transmittancemeasurement system can operate at a second wavelength distinct from thefirst wavelength. For example, in some embodiments, the secondwavelength can be a wavelength at which the one or more opaque regionsof the chamber windows, although opaque for the first wavelength, arenot opaque for the second wavelength, such that radiation at the firstwavelength is blocked by the opaque regions and radiation at the secondwavelength is at least partially allowed through the opaque regions. Forexample, transmittance of the opaque regions at the second wavelengthcan be greater than transmittance at the first wavelength. In someembodiments, the second wavelength can be 2.3 micrometers.

In some cases, it can be desirable and/or necessary to use a secondwavelength for the transmittance measurement system that is not entirelyshielded by the chamber windows. For example, spatial considerations,interference considerations, and/or other factors can cause a thermalprocessing system at the first wavelength to be undesirable. As oneexample, although the emissivity measurement system can include atransmittance measurement used to determine the emissivity, which couldbe correlated to temperature of the workpiece, it can sometimes bedesirable to obtain temperature measurements at multiple regions of theworkpiece. For instance, obtaining temperature measurements at multipleregions, such as a center portion and/or an edge portion, can allow forimproved monitoring of process uniformity. However, additional sensorscan be required to obtain the temperature measurements over multipleregions. Furthermore, the transmittance measurement can require emittersto be placed opposite the additional sensors, which can, in some cases,also require transparent regions to be disposed within a field of viewof the emitters for the transmittance measurements to function at thefirst wavelength. In some embodiments, however, these additional sensorscan, in addition to being used for a transmittance measurement, be usedfor an emission measurement in accordance with example aspects of thepresent disclosure. These transparent regions can, in some cases,contribute to contamination from the heating lamps in the measurementsfrom the additional sensors, especially in cases where the sensors areused for emission measurements. Thus, although one method to solve thisproblem is to configure the chamber with additional transparent regions,other solutions can be employed, including phase-locking of theemissions and/or sensor measurements, as discussed in more detail below.

In some embodiments, the plurality of infrared emitters and/or theplurality of infrared sensors can be phase-locked. For instance, in someembodiments, radiation emitted by one or more emitters can be pulsed ata pulsing frequency. The pulsing frequency can be selected to be orinclude a frequency having little to no radiation components in thethermal processing system. For example, in some embodiments, the pulsingfrequency can be about 130 Hz. In some embodiments, a pulsing frequencyof 130 Hz can be particularly advantageous as the heating lamps can emitsubstantially no radiation having a frequency of 130 Hz. As one exampleof pulsing one or more emitters, a chopper wheel having one or moreslits can be revolved in a field of view of the one or more emitters,such that a constant stream of radiation from the one or more emittersis intermittently allowed, at the pulsing frequency, past the chopperwheel. Thus, the constant stream of radiation can be converted by therevolution of the chopper wheel into a pulsed radiation stream at thepulsing frequency.

Additionally and/or alternatively, one or more sensors can bephase-locked based on the pulsing frequency. For example, thetransmittance measurement system can be configured to isolate ameasurement from a sensor based on the pulsing frequency. As oneexample, the transmittance measurement system can compare measurementsat the pulsing frequency to measurements not at the pulsing frequency,such as by subtracting a measurement immediately prior to themeasurement made at the pulsing frequency to isolate signalcontributions from components at the pulsing frequency from interferingcomponents. In other words, sensor measurements that are notphase-locked to the pulsing frequency (e.g., obtained with the same orgreater frequency than the pulsing frequency and/or out of phase withthe phase-locked measurements) can be indicative of only stray radiationin the chamber and/or sensor measurements that are phase-locked to thepulsing frequency can be indicative of a sum of stray radiation andemitted radiation from an emitter. Thus, the emitted radiation can beisolated by subtracting out the known amount of stray radiation from ameasurement that is not phase-locked. As one example, if the pulsingfrequency is 130 Hz, the sensor can obtain measurements at 260 Hz orgreater, such that one or more stray intensity measurements areassociated with each phase-locked measurement. In this way, thetransmittance measurement system can reduce interference from strayradiation (e.g., stray light) in measurements from a sensor.

Systems and methods according to example aspects of the presentdisclosure can provide a number of technical effects and benefitsrelated to thermal processing of a workpiece. As one example, systemsand methods according to example aspects of the present disclosure canprovide accurate temperature measurements at workpiece temperatures atwhich a workpiece is substantially transparent and/or does not emitsignificant blackbody radiation. For instance, systems and methodsaccording to example aspects of the present disclosure can allow foraccurate temperature measurement below about 600° C. regardless ofworkpiece composition.

Another technical effect of the present disclosure can be an improvedrange of temperature measurement. For instance, systems according toexample aspects of the present disclosure can allow for accuratetransmittance-based and emissivity-compensated temperature measurementof a workpiece at low temperatures, such as below about 600° C., such asfrom about 400° C. to 600° C. Additionally, sensors used in obtainingthe transmittance-based temperature measurement for workpiecetemperatures below about 600° C. can be repurposed and/or also used foremission-based temperature measurement of a workpiece for workpiecetemperatures at which the workpiece is substantially opaque and/or emitssignificant blackbody radiation, such as above about 600° C.Additionally, measurement wavelengths and/or other process aspects,including phase-locking of certain measurements, can be selected tominimize interference between various functions of the thermalprocessing systems. This can allow for systems and methods according toexample aspects of the present disclosure to measure temperatures overan increased range, such as an increased range including temperaturesbelow about 600° C., compared to conventional systems and methods.Additionally, this can allow systems and methods to smoothly transitionfrom a transmittance-based temperature measurement for temperatures atwhich the workpiece does not emit practically measurable blackbodyradiation (e.g., below about 600° C.) to an emission-based temperaturemeasurement for temperatures at which the workpiece emits measurableradiation (e.g., above about 600° C.) without requiring additionalsensors and/or reconfiguration of the sensors, as the same sensors usedfor the transmittance-based temperature measurement can be used for theemission-based temperature measurement, such as once the workpiece is nolonger at least partially transparent.

Variations and modifications can be made to these example embodiments ofthe present disclosure. As used in the specification, the singular forms“a,” “and,” and “the” include plural referents unless the contextclearly dictates otherwise. The use of “first,” “second,” “third,” etc.,are used as identifiers and are not necessarily indicative of anyordering, implied or otherwise. Example aspects may be discussed withreference to a “substrate,” “workpiece,” or “workpiece” for purposes ofillustration and discussion. Those of ordinary skill in the art, usingthe disclosures provided herein, will understand that example aspects ofthe present disclosure can be used with any suitable workpiece. The useof the term “about” in conjunction with a numerical value refers towithin 20% of the stated numerical value.

With reference now to the FIGS., example embodiments of the presentdisclosure will now be discussed in detail. FIG. 1 depicts an examplerapid thermal processing (RTP) system 100 according to exampleembodiments of the present disclosure. As illustrated, the RTP system100 includes an RTP chamber 105 including a top 101 and bottom 102,windows 106, 108, workpiece 110, workpiece support plate 120, heatsources 130, 140 (e.g., heating lamps), infrared emitters 150, 152, 154,sensors 165, 166, 167, 168 (e.g., pyrometers, such as dual-headpyrometers), controller 175, sidewall/door 180, and gas flow controller185.

The workpiece 110 to be processed is supported in the RTP chamber 105(e.g., a quartz RTP chamber) by the workpiece support plate 120. Theworkpiece support plate 120 can be a workpiece support operable tosupport a workpiece 110 during thermal processing. Workpiece 110 can beor include any suitable workpiece, such as a semiconductor workpiece,such as a silicon workpiece. In some embodiments, workpiece 110 can beor include a lightly doped silicon workpiece. For example, a lightlydoped silicon workpiece can be doped such that a resistivity of thesilicon workpiece is greater than about 0.1 Ωcm, such as greater thanabout 1 Ωcm.

Workpiece support plate 120 can be or include any suitable supportstructure configured to support workpiece 110, such as to supportworkpiece 110 in RTP chamber 105. In some embodiments, workpiece supportplate 120 can be configured to support a plurality of workpieces 110 forsimultaneous thermal processing by a thermal processing system. In someembodiments, workpiece support plate 120 can rotate workpiece 110before, during, and/or after thermal processing. In some embodiments,workpiece support plate 120 can be transparent to and/or otherwiseconfigured to allow at least some electromagnetic radiation to at leastpartially pass through workpiece support plate 120. For instance, insome embodiments, a material of workpiece support plate 120 can beselected to allow desired electromagnetic radiation to pass throughworkpiece support plate 120, such as electromagnetic radiation that isemitted by workpiece 110 and/or emitters 150, 152, 154. In someembodiments, workpiece support plate 120 can be or include a quartzmaterial, such as a hydroxyl free quartz material.

Workpiece support plate 120 can include at least one support pin 115extending from workpiece support plate 120. In some embodiments,workpiece support plate 120 can be spaced from top plate 116. In someembodiments, the support pins 115 and/or the workpiece support plate 120can transmit heat from heat sources 140 and/or absorb heat fromworkpiece 110. In some embodiments, the support pins 115, guard ring109, and top plate 116 can be made of quartz.

A guard ring 109 can be used to lessen edge effects of radiation fromone or more edges of the workpiece 110. Sidewall/door 180 allows entryof the workpiece 110 and, when closed, allows the chamber 105 to besealed, such that thermal processing can be performed on workpiece 110.For example, a process gas can be introduced into the RTP chamber 105.Two banks of heat sources 130, 140 operable to heat the workpiece 110 inthe RTP chamber 105 (e.g., lamps, or other suitable heat sources) areshown on either side of the workpiece 110. Windows 106, 108 can beconfigured to block at least a portion of radiation emitted by the heatsources 130, 140, as described more particularly below.

RTP system 100 can include heat sources 130, 140. In some embodiments,heat sources 130, 140 can include one or more heating lamps. Forexample, heat sources 130, 140 including one or more heating lamps canemit electromagnetic radiation (e.g., broadband electromagneticradiation) to heat workpiece 110. In some embodiments, for example, heatsources 130, 140 can be or include arc lamps, tungsten-halogen lamps,and/or any other suitable heating lamp, and/or combination thereof. Insome embodiments, directive elements (not depicted) such as, forexample, reflectors (e.g., mirrors) can be configured to directelectromagnetic radiation from heat sources 130, 140 into RTP chamber105.

According to example aspects of the present disclosure, windows 106, 108can be disposed between workpiece 110 and heat sources 130, 140. Windows106, 108 can be configured to selectively block at least a portion ofelectromagnetic radiation (e.g., broadband radiation) emitted by heatsources 130, 140 from entering a portion of rapid thermal processingchamber 105. For example, windows 106, 108 can include opaque regions160 and/or transparent regions 161. As used herein, “opaque” meansgenerally having a transmittance of less than about 0.4 (40%) for agiven wavelength, and “transparent” means generally having atransmittance of greater than about 0.4 (40%) for a given wavelength.

Opaque regions 160 and/or transparent regions 161 can be positioned suchthat the opaque regions 160 block stray radiation at some wavelengthsfrom the heat sources 130, 140, and the transparent regions 161 allow,for example, emitters 150, 152, 154 and/or sensors 165, 166, 167, 168 tofreely interact with radiation in RTP chamber 105 at the wavelengthsblocked by opaque regions 160. In this way, the windows 106, 108 caneffectively shield the RTP chamber 105 from contamination by heatsources 130, 140 at given wavelengths while still allowing the heatsources 130, 140 to heat workpiece 110. Opaque regions 160 andtransparent regions 161 can generally be defined as opaque andtransparent, respectively, to a particular wavelength; that is, for atleast electromagnetic radiation at the particular wavelength, the opaqueregions 160 are opaque and the transparent regions 161 are transparent.

Chamber windows 106, 108, including opaque regions 160 and/ortransparent regions 161, can be formed of any suitable material and/orconstruction. In some embodiments, chamber windows 106, 108 can be orinclude a quartz material. Furthermore, in some embodiments, opaqueregions 160 can be or include hydroxyl (OH) containing quartz, such ashydroxyl doped quartz (e.g., quartz that is doped with hydroxyl), and/ortransparent regions 161 can be or include hydroxyl free quartz (e.g.,quartz that is not doped with hydroxyl). Advantages of hydroxyl dopedquartz and hydroxyl free quartz can include an ease of manufacturing.For instance, the hydroxyl free quartz regions can be shielded duringhydroxyl doping of a monolithic quartz window to produce both hydroxyldoped regions (e.g., opaque regions) and hydroxyl free regions (e.g.,transparent regions) in the monolithic window. Additionally, hydroxyldoped quartz can exhibit desirable wavelength blocking properties inaccordance with the present disclosure. For instance, hydroxyl dopedquartz can block radiation having a wavelength of about 2.7 micrometers,which can correspond to a measurement wavelength at which some sensors(e.g., sensors 165, 166, 167, 168) in the thermal processing system 100operate, while hydroxyl free quartz can be transparent to radiationhaving a wavelength of about 2.7 micrometers. Thus, the hydroxyl dopedquartz regions can shield the sensors (e.g., sensors 165, 166, 167, 168)from stray radiation in the rapid thermal processing chamber 105 (e.g.,from heat sources 130, 140), and the hydroxyl free quartz regions can bedisposed at least partially within a field of view of the sensors toallow the sensors to obtain measurements within the thermal processingsystem. Additionally, hydroxyl doped quartz can be partially opaque(e.g., have a transmittance around 0.6, or 60%) to radiation having awavelength of about 2.3 micrometers, which can at least partially reducecontamination from stray radiation in rapid thermal processing system100 (e.g., from heat sources 130, 140).

Gas controller 185 can control a gas flow through RTP system 100, whichcan include an inert gas that does not react with the workpiece 110and/or a reactive gas such as oxygen or nitrogen that reacts with thematerial of the workpiece 110 (e.g. a semiconductor workpiece, etc.) toform a layer of on the workpiece 110. In some embodiments, an electricalcurrent can be run through the atmosphere in RTP system 100 to produceions that are reactive with or at a surface of workpiece 110, and toimpart extra energy to the surface by bombarding the surface withenergetic ions.

The controller 175 controls various components in RTP chamber to directthermal processing of workpiece 110. For example, controller 175 can beused to control heat sources 130 and 140. Additionally and/oralternatively, controller 175 can be used to control the gas flowcontroller 185, the door 180, and/or a temperature measurement system,including, for instance, emitters 150, 152, 154 and/or sensors 165, 166,167, 168. The controller 175 can be configured to measure a temperatureof the workpiece, which will be discussed more particularly with respectto the following figures. For instance, FIG. 2 depicts a thermalprocessing system 200 including one or more components of thermalprocessing system 100 configured to perform in-situ emissivitydetermination of a workpiece. FIG. 3 depicts at least a thermalprocessing system 300 including one or more components of thermalprocessing system 100 configured to perform transmittance-based and/oremission-based temperature measurement of a workpiece. Similarly, FIG. 4depicts a temperature measurement system 400 including one or morecomponents of thermal processing system 100 configured to performtransmittance-based and/or emission-based temperature measurement of aworkpiece.

As used herein, a controller, control system, or similar can include oneor more processors and one or more memory devices. The one or moreprocessors can be configured to execute computer-readable instructionsstored in the one or more memory devices to perform operations, such asany of the operations for controlling a thermal processing systemdescribed herein.

FIG. 1 depicts an example thermal processing system 100 for purposes ofillustration and discussion. Those of ordinary skill in the art, usingthe disclosures provided herein, will understand that aspects of thepresent disclosure can be used with other thermal processing systems forworkpieces without deviating from the scope of the present disclosure.

FIG. 2 depicts an example thermal processing system 200 for purposes ofillustration and discussion. In particular, thermal processing systemincludes one or more components as discussed with respect to thermalprocessing system 100 of FIG. 1 FIG. 1 . In particular, FIG. 2 depictsat least components useful in determining an in-situ emissivitymeasurement of workpiece 110, including at least emitter 150 and sensors165 and 166. As depicted in FIG. 2 , emitter 150 can be configured toemit infrared radiation directed at an oblique angle to workpiece 110. Atransmitted portion of the emitted radiation emitted by emitter 150 istransmitted through workpiece 110 and incident on transmittance sensor165. A reflected portion of the emitted radiation emitted by emitter 150is reflected by workpiece 110 and incident on reflectance sensor 166. Anemissivity of the workpiece can be determined by the transmitted portionand the emitted portion. For example, the transmittance of workpiece 110can be represented by the intensity of radiation incident ontransmittance sensor 165. Additionally, the reflectance of workpiece 110can be represented by the intensity of radiation incident on reflectancesensor 166. From transmittance and reflectance, transmissivity τ andreflectivity ρ can be determined as a ratio of transmittance andreflectance, respectively, to a reference intensity I₀ which canrepresent intensities at the sensors 165, 166 when no workpiece ispresent in the thermal processing system 200. From that, emissivity ϵcan be calculated as:

ϵ=1−(ρ+τ)

According to example aspects of the present disclosure, one or moretransparent regions 161 can be disposed at least partially in a field ofview of emitter 150 and/or sensors 165, 166. For instance, emitter 150and/or sensors 165, 166 can operate at a measurement wavelength rangethat the transparent regions 161 are transparent to. For example, insome embodiments, emitter 150 and/or sensors 165, 166 can operate at 2.7micrometers. As illustrated in FIG. 2 , the transparent regions 161 canbe positioned such that a radiation flow (indicated generally by arrows)is able to flow from emitter 150 through the transparent regions 161 andto sensors 165, 166, without obstruction by windows 106, 108 (e.g.,opaque regions 160). Similarly, opaque regions 160 can be disposed inregions on windows 106, 108 that are outside of the radiation flow toshield workpiece 110 and especially sensors 165, 166 from radiation inthe measurement wavelength range from heat sources 130, 140. Forexample, in some embodiments, transparent regions 161 can be includedfor sensors and/or emitters operating at 2.7 micrometer wavelengths.

In some embodiments, emitter 150 and/or sensors 165, 166 can bephase-locked. For instance, in some embodiments, emitter 150 and/orsensors 165, 166 can be operated according to a phase-locked regime. Forinstance, although opaque regions 160 can be configured to block moststray radiation from heat sources 130, 140 at a first wavelength, insome cases stray radiation can nonetheless be perceived by the sensors165, 166, as discussed above. Operating the emitter 150 and/or sensors165, 166 according to a phase-locked regime can contribute to improvedaccuracy in intensity measurements despite the presence of strayradiation.

For instance, in some embodiments, radiation emitted by emitter 150 canbe pulsed at a pulsing frequency. The pulsing frequency can be selectedto be or include a frequency having little to no radiation components inthe thermal processing system 200. For example, in some embodiments, thepulsing frequency can be about 130 Hz. In some embodiments, a pulsingfrequency of 130 Hz can be particularly advantageous as the heat sources130, 140 can emit substantially no radiation having a frequency of 130Hz. Additionally and/or alternatively, sensors 165, 166 can bephase-locked based on the pulsing frequency. For instance, the thermalprocessing system 200 (e.g., a controller, such as controller 175 ofFIG. 1 ), can isolate a measurement (e.g., an intensity measurement)from the sensors 165, 166 based on the pulsing frequency. In this way,thermal processing system 200 can reduce interference from strayradiation in measurements from sensors 165, 166.

An example phase locking regime is discussed with respect to plots 250,255, 260. Plot 250 depicts radiation intensity for radiation I_(IR)emitted within the measurement wavelength range by emitter 150 over time(e.g., over a duration of a thermal process performed on workpiece 110).As illustrated in plot 250, radiation intensity emitted by emitter 150can be emitted as pulses 251. For instance, emitter 150 can be pulsed bya chopper wheel (not illustrated). A chopper wheel can include one ormore blocking portions and/or one or more passing portions. A chopperwheel can be revolved in a field of view of emitter 150 such that aconstant stream of radiation from emitter 150 is intermittentlyinterrupted by blocking portions and passed by passing portions at thepulsing frequency. Thus, a constant stream of radiation emitted byemitter 150 can be converted by the revolution of a chopper wheel into apulsed radiation stream at the pulsing frequency.

Plot 255 depicts transmitted radiation intensity I_(T) measured bytransmittance sensor 165 over time. Similarly, plot 260 depictsreflected radiation intensity I_(R) measured by reflectance sensor 166over time. Plots 255 and 260 illustrate that, over time (e.g., asworkpiece 110 increases in temperature), stray radiation in the chamber(illustrated by stray radiation curves 256 and 261, respectively) canincrease. This can be attributable to, for example, decreasingtransparency of workpiece 110 and/or increasing emissions of workpiece110 with respect to an increased temperature of the workpiece 110,increased intensity of the heat sources 130, 140, and/or various otherfactors related to thermal processing of workpiece 110.

During a point in time at which the emitter 150 is not emittingradiation, the sensors 165, 166 can obtain measurements corresponding tothe stray radiation curves 256, 261, respectively (e.g., stray radiationmeasurements). Similarly, during a point in time at which the emitter150 is emitting radiation (e.g., pulse 251), the sensors 165, 166 canobtain measurements corresponding to total radiation curves 257, 262,respectively (e.g., total radiation measurements). Thus, transmittedradiation intensity I_(T) (e.g., attributable to transmittance T) can bedetermined based at least in part the difference betweentime-coordinated (e.g., subsequent) total radiation measurements (e.g.,representing curve 256) and stray radiation measurements (e.g.,representing curve 256). Furthermore, transmittance τ can be determinedby a ratio of the transmitted radiation intensity IT to a referenceintensity I₀. Similarly, reflected radiation intensity I_(R) (e.g.,attributable to reflectance ρ) can be determined based at least in partthe difference between time-coordinated (e.g., subsequent) totalradiation measurements (e.g., representing curve 262) and strayradiation measurements (e.g., representing curve 261). Furthermore,reflectance ρ can be determined by a ratio of the reflected radiationintensity IR to reference intensity I₀. In some embodiments, referenceintensity I₀ can be measured by sensors 165, 166 as a result of a pulseand/or constant radiation from emitter 150 when no workpiece 110 ispresent in thermal processing system 200. From the transmittance τ andreflectance ρ, the emissivity c can be calculated by:

ϵ=1−(ρ+τ)

FIG. 3 depicts an example thermal processing system 300 according toexample aspects of the present disclosure. Thermal processing system 300can be configured to perform thermal processing on and/or to measure atemperature of workpiece 110. In particular, thermal processing systemcan include one or more components as discussed with respect to thermalprocessing system 100 of FIG. 1 FIG. 1 . In particular, FIG. 3 depictsat least components useful in determining a transmittance-based and/oremission-based temperature measurement of workpiece 110, including atleast center emitter 152 and center sensor 167. In some embodiments,edge emitter 154 and/or edge sensor 168 can operate similarly to centeremitter 152 and/or center sensor 154 on an edge portion of workpiece110, as discussed with respect to FIG. 3 , but are omitted from beingdepicted in FIG. 3 for the purposes of illustration. This is discussedfurther below with respect to FIG. 4 .

As depicted in FIG. 3 , center emitter 152 can be configured to emitinfrared radiation directed at an orthogonal angle to a surface ofworkpiece 110, as illustrated by the arrow in FIG. 3 . A transmittedportion of radiation emitted by center emitter 152 is transmittedthrough workpiece 110 and incident on center sensor 167. In someembodiments, transparent regions 161 of windows 106, 108 can be disposedwithin a field of view of center emitter 152 and/or sensor 167. Forinstance, center emitter 152 and/or center sensor 167 can operate at ameasurement wavelength range that the transparent regions 161 aretransparent to. For example, in some embodiments, center emitter 152and/or center sensor 167 can operate at 2.7 micrometers. As illustratedin FIG. 3 , the transparent regions 161 can be positioned such that aradiation flow (indicated generally by arrows) is able to flow fromcenter emitter 152 through the transparent regions 161 and to centersensor 167, without obstruction by windows 106, 108 (e.g., opaqueregions 160). Similarly, opaque regions 160 can be disposed in regionson windows 106, 108 that are outside of the radiation flow to shieldworkpiece 110 and especially center sensor 167 from radiation in themeasurement wavelength range from heat sources 130, 140. For example, insome embodiments, transparent regions 161 can be included for sensorsand/or emitters operating at 2.7 micrometer wavelengths.

In some embodiments, however, including transparent regions 161 inwindows 106 disposed within a field of view of center emitter 152 canundesirably allow radiation emitted by heat sources 130 to contaminatemeasurements by center sensor 167 and/or other sensors (not illustrated)in thermal processing system 300. For example, in some embodiments,center sensor 167 can additionally be configured to measure thermalradiation emitted by workpiece 110 at a measurement wavelength range forwhich the transparent regions 161 are transparent. Radiation emitted byheat sources 130 can have an increased risk of contaminating thisworkpiece emission measurement if transparent regions 161 are disposedin a field of view of center emitter 152.

One solution to this problem is to omit transparent region 161 in afield of view of center emitter 152 and instead include an opaque region160. Additionally, center emitter 152 and/or center sensor 167 can beoperated at a second wavelength in a measurement wavelength range forwhich opaque region 160 is at least partially transparent. For example,in some embodiments, the second wavelength can be 2.3 micrometers. Inthis way, despite the presence of opaque region 160, radiation emittedby center emitter 152 can pass through the windows 106 and 108 and bemeasured by center sensor 167 without requiring the inclusion ofpotentially contaminating transparent regions. Furthermore, because ofthe inclusion of opaque region 160, measurements from center sensor 167indicative of an intensity of emitted radiation (e.g., emitted radiationmeasurements) emitted by workpiece 110 (e.g., at temperatures at whichworkpiece 110 emits radiation, such as above about 600° C.) are notcontaminated by the stray radiation. The above discussed solution canintroduce an additional problem, however. Because the radiation at thesecond wavelength from center emitter 152 is able to pass through opaqueregions 160, so too can stray radiation at the second wavelength from,for example, heat sources 130, 140.

Thus, in some embodiments, center emitter 152 and/or center sensor 167can be phase-locked. In some embodiments, center emitter 152 and/orcenter sensor 167 can be operated according to a phase-locked regime.For instance, although opaque regions 160 can be configured to blockmost stray radiation from heat sources 130, 140 at a first wavelength,in some cases stray radiation, especially stray radiation at a secondwavelength, can nonetheless be perceived by the center sensor 167, asdiscussed above. Operating the center emitter 152 and/or center sensor167 according to a phase-locked regime can contribute to improvedaccuracy in intensity measurements despite the presence of strayradiation.

For instance, in some embodiments, radiation emitted by center emitter152 can be pulsed at a pulsing frequency. The pulsing frequency can beselected to be or include a frequency having little to no radiationcomponents in the thermal processing system 300. For example, in someembodiments, the pulsing frequency can be about 130 Hz. In someembodiments, a pulsing frequency of 130 Hz can be particularlyadvantageous as the heat sources 130, 140 can emit substantially noradiation having a frequency of 130 Hz. Additionally and/oralternatively, center sensor 167 can be phase-locked based on thepulsing frequency. For instance, the thermal processing system 300(e.g., a controller, such as controller 175 of FIG. 1 ), can isolate ameasurement (e.g., an intensity measurement) from the center sensor 167based on the pulsing frequency. In this way, thermal processing system300 can reduce interference from stray radiation in measurements fromcenter sensor 167.

An example phase locking regime is discussed with respect to plots 310and 320. Plot 310 depicts radiation intensity for radiation I_(IR)emitted within the measurement wavelength range by center emitter 152over time (e.g., over a duration of a thermal process performed onworkpiece 110). Plot 320 depicts transmitted radiation intensity I_(T)measured by center sensor 167 over time. As illustrated in plot 310,radiation intensity emitted by center emitter 152 can be emitted aspulses 311. For instance, center emitter 152 can be pulsed by chopperwheel 302. Chopper wheel 302 can include one or more blocking portions305 and/or one or more passing portions 306. Chopper wheel 302 can berevolved in a field of view of center emitter 152 such that a constantstream of radiation from center emitter 152 is intermittentlyinterrupted by blocking portions 305 and passed by passing portions 306at the pulsing frequency. Thus, a constant stream of radiation emittedby center emitter 152 can be converted by the revolution of chopperwheel 302 into a pulsed radiation stream at the pulsing frequency.

During a point in time at which the center emitter 152 is not emittingradiation, the center sensor 167 can obtain measurements correspondingto the stray radiation curve 312 (e.g., stray radiation measurements).Similarly, during a point in time at which the center emitter 152 isemitting radiation (e.g., pulse 311), the center sensor 167 can obtainmeasurements corresponding to a total radiation curve 313 (e.g., totalradiation measurements). Thus, transmitted radiation intensity I_(T)(e.g., attributable to transmittance τ) can be determined based at leastin part the difference between time-coordinated (e.g., subsequent) totalradiation measurements (e.g., representing curve 313) and strayradiation measurements (e.g., representing curve 312). Furthermore,transmittance T can be determined by a ratio of the transmittedradiation intensity I_(T) to a reference intensity Io. For example,reference intensity I₀ can be measured by center sensor 167 as a resultof a pulse and/or constant radiation from center emitter 152 when noworkpiece 110 is present in thermal processing system 300. Thetransmittance τ can be compared to a transmittance curve (e.g.,workpiece transmittance curves 602, 604, 606 of FIG. 6A that arerespective to a particular workpiece composition, and/or normalizedworkpiece transmittance curve 652 of FIG. 6B) to determine a temperatureof the workpiece.

Plot 320 illustrates that, over time (e.g., as workpiece 110 increasesin temperature), stray radiation in the chamber (illustrated by strayradiation curve 312) can increase. This can be attributable to, forexample, decreasing transparency of workpiece 110 and/or increasingemissions of workpiece 110 with respect to an increased temperature ofthe workpiece 110, increased intensity of the heat sources 130, 140,and/or various other factors related to thermal processing of workpiece110. For instance, as can be seen in plot 320, stray radiation curve 312and total radiation curve 313 tend to converge as time progresses (e.g.,as temperature increases). This can be a result of, for example,decreasing transparency of workpiece 110 with respect to increasingtemperature. Thus, in some cases (e.g., for silicon workpieces), thetransmittance-based temperature measurement as described above canexhibit decreased reliability above a certain temperature (e.g., about600° C.). Thus, according to example aspects of the present disclosure,a thermal processing system (e.g., any of thermal processing systems100, 200, 300) can transition from a first temperature measurementprocess (e.g., a transmittance-based temperature measurement process) toa second temperature measurement process (e.g., an emission-basedtemperature measurement process) at a temperature threshold. Forexample, the temperature threshold can be about 600° C. The temperaturethreshold can correspond to a workpiece temperature at which theworkpiece 110 exhibits substantial blackbody radiation at a wavelengththat can be detected by center sensor 167. Additionally and/oralternatively, the temperature threshold can correspond to a workpiecetemperature at which the workpiece 110 is opaque to radiation emitted bycenter emitter 152. For instance, in some embodiments, the temperaturethreshold can correspond to a point at which stray radiation curve 312and total radiation curve 313 have converged, or, in other words, themagnitude of transmitted radiation intensity I_(T) is below a magnitudethreshold.

For instance, in some embodiments, center sensor 167 can be configuredto measure radiation emitted by workpiece 110 at the measurementwavelength range. For example, in some embodiments, center sensor 167can be a dual head pyrometer having a first head configured to measure afirst wavelength of a measurement wavelength range. The first wavelengthcan be or include a wavelength that transparent regions 161 aretransparent to and/or opaque regions 160 are opaque to, such as, forexample, 2.7 micrometers, in embodiments where the opaque regions 160include hydroxyl doped quartz. The first wavelength can additionallycorrespond to a wavelength of blackbody radiation emitted by workpiece110. Additionally, center sensor 167 can have a second head configuredto measure a second wavelength of the measurement wavelength range. Thesecond wavelength can be or include a wavelength that opaque regions 160are not opaque to, such as, for example, 2.3 micrometers, in embodimentswhere the opaque regions 160 include hydroxyl doped quartz. The secondwavelength can additionally correspond to a wavelength emitted by centeremitter 152.

Thus, according to example aspects of the present disclosure, centersensor 167 can obtain transmittance measurements associated withtransmittance of workpiece 110 for temperatures of workpiece 110 below atemperature threshold, and can additionally obtain emission measurementsassociated with an intensity of blackbody radiation emitted by workpiece110 for temperatures above the temperature threshold. Thus, temperatureof workpiece 110 can be determined by transmittance measurements attemperatures below a temperature threshold, as described above.Additionally and/or alternatively, temperature of workpiece 110 can bedetermined by emission measurements at temperatures above a temperaturethreshold. For instance, temperature of a workpiece can be determined byemission measurements based on the following equation:

$T = {\frac{hc}{\lambda k} \cdot \frac{1}{\ln\left( {{\frac{2\pi{hc}^{2}\Delta\lambda}{\lambda^{5}} \cdot \frac{\varepsilon}{I_{Wafer}}} + 1} \right)}}$

FIG. 4 depicts an example temperature measurement system 400 accordingto example aspects of the present disclosure. Temperature measurementsystem 400 can be configured to measure a temperature of workpiece 110,which can be supported at least in part by support ring 109. Temperaturemeasurement system 400 can include center emitter 152 and edge emitter154. Additionally, temperature measurement system 400 can include centersensor 167 and edge sensor 168. Emitters 152, 154 and/or sensors 167,168 can operate as discussed with regard to center emitter 152 and/orcenter sensor 168 of FIG. 3 . For instance, center emitter 152 andcenter sensor 167 can be disposed such that radiation emitted by centeremitter 152 passes through center portion 111 of workpiece 110 and isthen incident on center sensor 167. Similarly, edge emitter 154 and edgesensor 168 can be disposed such that radiation emitted by edge emitter154 passes through edge portion 112 of workpiece 110 and is incident onedge sensor 168. In this way, center sensor 167 can be configured toobtain a temperature measurement of center portion 111 and/or edgesensor 168 can be configured to obtain a temperature measurement of edgeportion 112. In some embodiments, center portion 111 can include aportion of the workpiece defined by less than about 50% of a radius r ofthe workpiece, such as about 10% of the radius r. In some embodiments,edge portion can include a portion of the workpiece defined by greaterthan about 50% of a radius r of the workpiece, such as about 90% of theradius r.

FIG. 5A depicts a plot 500 of an example transmittance curve 502 for anexample material composing an example opaque region. For example,transmittance curve 502 is illustrated for an example material such ashydroxyl doped quartz. As illustrated in FIG. 5A, the example opaqueregion can be substantially opaque to some wavelengths and substantiallytransparent to others. In particular, the example transmittance curve502 includes an opaque range 504 and a partially opaque range 506. Asdiscussed herein, a measurement wavelength range can advantageouslyinclude wavelengths in the opaque range 504 and/or partially opaquerange 506. For instance, radiation in the opaque range 504 and/orpartially opaque range 506 can be at least partially blocked by theexample opaque region, which can prevent radiation emitted by heatinglamps from entering a thermal processing chamber and contaminatingmeasurements from sensors configured to measure the opaque range 504and/or partially opaque range 506.

FIG. 5B depicts a plot 520 of an example transmittance curve 522 for anexample material composing an example transparent region. For example,transmittance curve 522 is illustrated for an example material such ashydroxyl free quartz. As illustrated in FIG. 5B, the example transparentregion can be substantially transparent over some wavelengths. Althoughthe example transmittance curve 522 is depicted as substantiallytransparent over most wavelengths, the example transparent region canadditionally include opaque ranges. Generally, it is desirable that theexample transparent region is transparent at measurement ranges (e.g.,at wavelengths corresponding to opaque range 504 and/or partially opaquerange 506 of FIG. 5A).

FIG. 6A depicts a plot 600 of example transmittance curves 602, 604, 606for three example workpiece types. For instance, curve 602 is associatedwith a workpiece having a lower reflectivity, curve 604 is associatedwith a workpiece having a moderate reflectivity (e.g., a bareworkpiece), and curve 606 is associated with a workpiece having a higherreflectivity. As illustrated in FIG. 6A, although each of curves 602,604, 606 follows a general trend, the values of the transmittance foreach workpiece can vary based on surface characteristics (e.g.,reflectivity) of the workpiece. Thus, FIG. 6B depicts a plot 650 of anexample normalized or nominal workpiece transmittance curve 652. Asillustrated in FIG. 6B, the normalized workpiece transmittance curve 652represents transmittance from a maximum of 1 to a minimum of 0 for aparticular workpiece, but is irrespective of a particular transmittancevalue of the workpiece. In other words, the normalized workpiecetransmittance curve 652 can be similar and/or identical for each of alow reflective workpiece, a bare workpiece, and/or a high reflectiveworkpiece. Thus, a normalized transmittance measurement obtained for aworkpiece can be compared to normalized workpiece transmittance curve652 such that transmittance can be directly correlated to temperature,irrespective of surface characteristics of a workpiece.

FIG. 7 depicts a flowchart of an example method 700 for measuring atemperature of a workpiece in a thermal processing system, such as, forexample, the thermal processing systems 100, 200, or 300 of FIGS. 1-3 .FIG. 7 depicts steps performed in a particular order for purposes ofillustration and discussion. Those of ordinary skill in the art, usingthe disclosures provided herein, will understand that various steps ofany of the methods described herein can be omitted, expanded, performedsimultaneously, rearranged, and/or modified in various ways withoutdeviating from the scope of the present disclosure. In addition, variousadditional steps (not illustrated) can be performed without deviatingfrom the scope of the present disclosure.

The method 700 can include, at 702, emitting, by one or more infraredemitters, infrared radiation directed at one or more surfaces of aworkpiece. For example, in some embodiments, one or more infraredemitters can emit radiation having a first wavelength and one or moreinfrared emitters can emit radiation having a second wavelength.

The method 700 can include, at 704, blocking, by one or more windows, atleast a portion of broadband radiation emitted by one or more heatinglamps configured to heat the workpiece from being incident on one ormore infrared sensors. For example, in some embodiments, the one or morewindows can block at least a portion of the broadband radiation that iswithin at least a portion of a measurement range.

The method 700 can include, at 706, measuring, by the one or moreinfrared sensors, a transmitted portion of the infrared radiationemitted by at least one of the one or more infrared emitters and passingthrough the one or more surfaces of the workpiece. For example, a firstportion of the transmitted portion can be incident on a firsttransmittance sensor to obtain a first transmittance measurement. Thefirst transmitted portion can correspond to an emitter and/or sensor ofan emissivity measurement system. The first transmitted portion can, insome embodiments, have an associated first wavelength. Additionallyand/or alternatively, a second portion of the transmitted portion can beincident on at least one second transmittance sensor to obtain at leastone second transmittance measurement. In some embodiments, the at leastone second transmittance sensor can additionally be configured tomeasure radiation emitted by a workpiece. In some embodiments, thesecond transmitted portion can have an associated second wavelength. Insome embodiments, the first wavelength can be blocked by the one or morewindows and/or the second wavelength can be at least partially passed bythe one or more windows. For example, in some embodiments, the firsttransmitted portion is associated with a first wavelength of themeasurement wavelength range and the second transmitted portion isassociated with a second wavelength of the measurement wavelength range,wherein the one or more windows block radiation at the first wavelengthand allow radiation at the second wavelength.

The method 700 can include, at 708, measuring, by the one or moreinfrared sensors, a reflected portion of the infrared radiation emittedby at least one of the one or more infrared emitters and reflected bythe one or more surfaces of the workpiece. For example, the reflectedportion can be incident on a reflectance sensor to obtain a reflectancemeasurement. In some embodiments, the reflectance sensor can be aportion of an emissivity measurement system.

In some embodiments, measuring, by the one or more infrared sensors, aportion of infrared radiation (e.g., a transmitted portion and/or areflected portion) emitted by at least one of the one or more infraredemitters can include phase-locking the one or more infrared sensorsand/or one or more infrared emitters. For example, phase-locking the oneor more infrared sensors and/or the one or more infrared emitters caninclude pulsing at least one of the one or more infrared emitters at apulsing frequency. As one example of pulsing one or more emitters, achopper wheel having one or more slits can be revolved in a field ofview of the one or more emitters, such that a constant stream ofradiation from the one or more emitters is intermittently allowed, atthe pulsing frequency, past the chopper wheel. Thus, the constant streamof radiation can be converted by the revolution of the chopper wheelinto a pulsed radiation stream at the pulsing frequency.

Additionally and/or alternatively, phase-locking the one or moreinfrared sensors and/or the one or more infrared emitters can includeisolating at least one measurement from the one or more infrared sensorsbased at least in part on the pulsing frequency. As one example,measurements from the one or more infrared sensors (e.g., measurementsindicative of an intensity of radiation incident on the one or moreinfrared sensors) that are at and/or in phase with the pulsing frequencycan be compared to measurements not at the pulsing frequency and/or outof phase with the measurements in phase with the pulsing frequency, suchas by subtracting subsequent measurements at double the pulsingfrequency. Thus, signal contributions from components at the pulsingfrequency (e.g., emitters) can be isolated from interfering components(e.g., stray radiation, such as heat lamps). In other words, sensormeasurements that are not phase-locked to the pulsing frequency (e.g.,obtained with the same or greater frequency than the pulsing frequencyand/or out of phase with the phase-locked measurements) can beindicative of only stray radiation in the chamber and/or sensormeasurements that are phase-locked to the pulsing frequency can beindicative of a sum of stray radiation and emitted radiation from anemitter. Thus, a measurement indicative of emitted radiation emitted bythe emitters can be isolated by subtracting out the amount of strayradiation indicated by a measurement that is not phase-locked. As oneexample, if the pulsing frequency is 130 Hz, the sensor can obtainmeasurements at 260 Hz or greater, such that one or more stray intensitymeasurements correspond to each phase-locked measurement. In this way,the thermal processing system can reduce interference from strayradiation (e.g., stray light) in measurements from a sensor.

The method 700 can include, at 710, determining, based at least in parton the transmitted portion and the reflected portion, a temperature ofthe workpiece. The temperature of the workpiece at 710 can be less thanabout 600° C. For example, in some embodiments, determining thetemperature of the workpiece can include determining, based at least inpart on the transmitted portion and the reflected portion, an emissivityof the workpiece, and determining, based at least in part on thetransmitted portion and the emissivity of the workpiece, the temperatureof the workpiece. For example, in some embodiments, the emissivity ofthe workpiece can be determined based at least in part on the firsttransmittance measurement and the reflectance measurement.

The method 700 can include, at 712, measuring, by the one or moreinfrared sensors, an emitted radiation measurement indicative ofinfrared radiation emitted by the workpiece. For example, the emittedradiation measurement can be indicative of an intensity of infraredradiation emitted by the workpiece and incident on the one or moresensors. According to example aspects of the present disclosure, theemitted radiation measurement can be obtained once the temperature ofthe workpiece is high enough such that the workpiece ceases to betransparent to infrared radiation from the emitters and/or begins toemit significant blackbody radiation at a wavelength configured to bemeasured by the one or more infrared sensors (e.g., within at least aportion of the measurement wavelength range).

In some embodiments, the emitted radiation measurement can correspond toa wavelength of infrared radiation that is blocked by the one or morewindows. For example, the emitted radiation measurement can correspondto a wavelength that is and/or is included in the portion of themeasurement wavelength range. For example, in some embodiments, theemitted radiation measurement can correspond to an intensity of infraredradiation having a wavelength of 2.7 micrometers.

The method 700 can include, at 714, determining, based at least in parton the emitted radiation measurement, the temperature of the workpiece.The temperature of the workpiece at 714 can be greater than about 600°C. For instance, determining the temperature of the workpiece greaterthan about 600° C. can include comparing the emitted radiationmeasurement to a blackbody radiation curve associated with theworkpiece. The blackbody radiation curve can correlate an intensity ofemitted blackbody radiation to temperature such that temperature can bedetermined based on a measured intensity (e.g., the emitted radiationmeasurement).

Systems implementing method 700 can experience an increased temperaturerange over which the temperature of the workpiece can be measured. Forinstance, the method 700 can include determining, based at least in parton the transmitted portion and the reflected portion, the temperature ofthe workpiece according to, for instance, steps 702-710 for temperaturesat which the emitted radiation measurement cannot be practicallyobtained (e.g., below about 600° C.). Additionally, the method 700 caninclude determining, based at least in part on the emitted radiationmeasurement, the temperature of the workpiece according to, forinstance, steps 712-714 for temperatures at which the emitted radiationmeasurement can be practically obtained (e.g., above about 600° C.).

FIG. 8 depicts a flowchart of an example method 800 for calibrating areference intensity for sensors in a thermal processing system, such as,for example, the thermal processing systems 100, 200, or 300 of FIGS.1-3 . FIG. 8 depicts steps performed in a particular order for purposesof illustration and discussion. Those of ordinary skill in the art,using the disclosures provided herein, will understand that varioussteps of any of the methods described herein can be omitted, expanded,performed simultaneously, rearranged, and/or modified in various wayswithout deviating from the scope of the present disclosure. In addition,various additional steps (not illustrated) can be performed withoutdeviating from the scope of the present disclosure.

The method 800 can include, at 802, emitting a first amount of infraredradiation from a respective emitter of the plurality of infraredemitters. The method 800 can include, at 804, determining a secondamount of infrared radiation incident on a respective sensor of theplurality of infrared sensors. The method 800 can include, at 806,determining the reference intensity associated with the respectiveemitter and the respective sensor based at least in part on a variationbetween the first amount and the second amount.

According to example aspects of the present disclosure, a referenceintensity, denoted herein as I₀, can be determined for each of one ormore sensors in a thermal processing system. A reference intensity cancorrespond to radiation emitted by an emitter and/or incident on asensor when a workpiece is not present in the processing chamber. Inother words, the reference intensity can be diminished from theintensity of radiation emitted by an emitter only by contributions fromcomponents other than the workpiece in the thermal processing system.This can additionally correspond to a case of 100% transmittance by aworkpiece. In some embodiments, the reference intensity can be measuredprior to insertion of a workpiece in the processing chamber, such asbetween thermal processing of two workpieces.

While the present subject matter has been described in detail withrespect to specific example embodiments thereof, it will be appreciatedthat those skilled in the art, upon attaining an understanding of theforegoing may readily produce alterations to, variations of, andequivalents to such embodiments. Accordingly, the scope of the presentdisclosure is by way of example rather than by way of limitation, andthe subject disclosure does not preclude inclusion of suchmodifications, variations and/or additions to the present subject matteras would be readily apparent to one of ordinary skill in the art.

1.-20. (canceled)
 21. A thermal processing system for performing thermalprocessing of a semiconductor workpiece, the thermal processing systemcomprising: a workpiece support plate configured to support a workpiece;one or more heat sources configured to heat the workpiece; a windowdisposed between the workpiece support plate and the one or more heatsources, the window comprising one or more transparent regions that aretransparent to at least a portion of electromagnetic radiation within ameasurement wavelength range; and a temperature measurement systemconfigured to obtain a temperature measurement indicative of atemperature of the workpiece, the temperature measurement systemcomprising: at least one infrared emitter configured to emit infraredradiation; at least one infrared sensor, the at least one infraredsensor configured to measure infrared radiation within the measurementwavelength range and disposed such that at least one of the one or moretransparent regions is at least partially within a field of view of theat least one infrared sensor; and a controller configured to performoperations, the operations comprising: obtaining, from the at least oneinfrared sensor, one or more first measurements associated with theworkpiece; determining, based at least in part on the one or more firstmeasurements, a temperature of the workpiece when the temperature of theworkpiece is less than about 600° C.
 22. The thermal processing systemof claim 21, wherein the operations further comprise: obtaining, fromthe at least one infrared sensor, one or more second measurementsassociated with the workpiece; and determining, based at least in parton the one or more second measurements, a temperature of the workpiecewhen the temperature of the workpiece is greater than about 600° C. 23.The thermal processing system of claim 22, wherein the one or more firstmeasurements are associated with a different optical measurement of theworkpiece relative to the one or more second measurements.
 24. Thethermal processing system of claim 22, wherein the one or more firstmeasurements associated with the workpiece comprise one or moretransmittance measurements and one or more reflectance measurements, 25.The thermal processing system of claim 24, wherein the one or moresecond measurements comprise one or more emission measurementsassociated with the workpiece.
 26. The thermal processing system ofclaim 21, wherein the at least one infrared emitter comprises a centeremitter operable to emit radiation towards a center portion of theworkpiece and an edge emitter operable to emit radiation towards an edgeportion of the workpiece, and wherein the at least one infrared sensorcomprises a center sensor corresponding to the center emitter and anedge sensor corresponding to the edge emitter.
 27. The thermalprocessing system of claim 21, wherein the one or more heat sources areconfigured to emit broadband radiation to heat the workpiece.
 28. Thethermal processing system of claim 27, wherein the window comprises oneor more opaque regions are configured to block at least a portion of thebroadband radiation emitted by the heat sources and within themeasurement wavelength range.
 29. The thermal processing system of claim28, wherein the one or more opaque regions comprise hydroxyl dopedquartz and wherein the one or more transparent regions comprise hydroxylfree quartz.
 30. The thermal processing system of claim 21, wherein theat least one infrared emitter is pulsed at a pulsing frequency.
 31. Thethermal processing system of claim 30, wherein the pulsing frequency is130 Hz.
 32. The thermal processing system of claim 21, wherein themeasurement wavelength range comprises at least one of 2.3 micrometersor 2.7 micrometers.
 33. The thermal processing system of claim 21,wherein the at least one infrared sensor comprises one or morepyrometers.
 34. The thermal processing system of claim 21, wherein theoperation of determining, based at least in part on the one or morefirst measurements, a temperature of the workpiece when the temperatureof the workpiece is less than about 600° C. comprises: determining,based at least in part on a first transmittance measurement and areflectance measurement, an emissivity of the workpiece; anddetermining, based at least in part on a second transmittancemeasurement and the emissivity of the workpiece, the temperature of theworkpiece.
 35. The thermal processing system of claim 34, wherein the atleast one first transmittance measurement and the at least onereflectance measurement are associated with a first wavelength of themeasurement wavelength range and the at least one second transmittancemeasurement is associated with a second wavelength of the measurementwavelength range.
 36. The thermal processing system of claim 21, whereinthe controller is configured to determine a reference intensity for atleast one of the plurality of infrared sensors when no workpiece ispresent in the workpiece processing system by performing operationscomprising: emitting a first amount of infrared radiation from the atleast one infrared emitter; determining a second amount of infraredradiation incident on the at least one infrared sensor; and determiningthe reference intensity associated with the at least one emitter and theat least one sensor based at least in part on a variation between thefirst amount of infrared radiation and the second amount of infraredradiation.
 37. A method for determining a temperature of a workpiece ina thermal processing system, the thermal processing system comprising aworkpiece support plate configured to support a workpiece; one or moreheat sources configured to heat the workpiece; a window disposed betweenthe workpiece support plate and the one or more heat sources, the windowcomprising one or more transparent regions that are transparent to atleast a portion of electromagnetic radiation within a measurementwavelength range; at least one infrared emitter configured to emitinfrared radiation; and at least one infrared sensor, the at least oneinfrared. sensor configured to measure infrared radiation within themeasurement wavelength range and disposed such that at least one of theone or more transparent regions is at least partially within a field ofview of the at least one infrared sensor, the method comprising:obtaining, from the at least one infrared sensor, one or more firstmeasurements associated with the workpiece; determining, based at leastin part on the one or more first measurements, a temperature of theworkpiece when the temperature of the workpiece is less than about 600°C.
 38. The method of claim 37, wherein the method further comprises:obtaining, from the at least one infrared sensor, one or more secondmeasurements associated with the workpiece; and determining, based atleast in part on the one or more second measurements, a temperature ofthe workpiece when the temperature of the workpiece is greater thanabout 600° C.